Memory effects in radiative jet energy loss

Abstract

In heavy-ion collisions the created quark-gluon plasma forms a quickly evolving background, leading to a time dependent radiative behavior of high momentum partons traversing the medium. We use the Schwinger Keldysh formalism to describe the jet evolution as a non-equilibrium process including the Landau-Pomeranschuk-Migdal effect. Concentrating on photon emission, a comparison of our results to a quasistatic calculation shows good agreement, leading to the conclusion that the radiative behavior follows the changes in the medium almost instantaneously

Classical model for diffusion and thermalization of heavy quarks in a hot medium: memory and out-of-equilibrium effects *

“…From the model discussed in this work we can interpret the lack of back-reaction as the lack of a drag coefficient in the equations of motion of the heavy quarks. While we recognize the need of a full numerical solution of the problem of the propagation of heavy quarks in the evolving Glasma we can use the present model, and in particular the estimate (58), to state that the pure diffusive approximation should work well as long as the initial kinetic energy of the heavy quark is small in comparison with the saturation scale. For example, taking Q s ≈ 2 GeV and an initial momentum P (0) = 2 GeV, which is a fair estimate of the initial average transverse momentum of heavy quarks produced via perturbative QCD [48], from Eq.…”

“…Furthermore, it will be interesting to study the impact of memory effect on heavy quark observables at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies, as well as on heavy quark thermalization time, which is neglected in several recent calculations [37][38][39][40][41][42]46]. It can be mentioned that memory effect have an important influence on the final dilepton yields [57] and radiative energy loss [58]. This indicates an analysis which describes the data correctly demands the inclusion of memory effects (for more see also [44,45,[54][55][56]).…”

“…The advantage of this model, despite its simplicity, is that it has the potential to describe several aspects that might be important to understand the drift and diffusion of these quarks, among them the propagation in a bath out of equilibrium like the Glasma, as well as the memory effects in the dissipation kernel. In the particular context of high energy nuclear collisions, memory has started to attract some interest [44,45,[54][55][56] as it might affect the dilepton yields [57] as well as radiative energy loss [58]. In this model, the bath is described as a system of harmonic oscillators; initial conditions for the oscillators are randomly assigned, with expectation values for the squared momenta and positions in agreement with the equipartition theorem in case of a bath in thermal equilibrium, or to the energy per particle in case the bath is out of equilibrium.…”

Off-equilibrium photon production during the chiral phase transition

“…This non-equilibrium dynamics has always been a major motivation for investigations on non-equilibrium quantum field theory [9,10,11,12,13,14,15,16,17,18,19,20]. Besides the role of possible memory effects during the time evolution [21,22,23,24,25,26,27,28,29], it is of particular interest how the finite lifetime QGP itself affects the resulting photon spectra.…”

Off-equilibrium photon production during the chiral phase transition

“…This non-equilibrium dynamics has always been a major motivation for investigations in non-equilibrium quantum field theory [9][10][11][12][13][14][15][16][17][18][19][20]. Besides the role of possible memory effects during the time evolution [21][22][23][24][25][26][27][28][29], it is of particular interest how the finite lifetime of the quark-gluon plasma itself affects the resulting photon spectra.…”